Bothrops pirajai snake venom L-amino acid oxidase: in vitro effects on infection of Toxoplasma gondii in human foreskin fibroblasts

The effect of an L-amino acid oxidase isolated from Bothrops pirajai snake venom (BpirLAAO-I) was investigated on infection of Toxoplasma gondii in human foreskin fibroblasts (HFF). The cytotoxic activity of BpirLAAO-I on HFF cells showed a dose-dependent toxicity with median cytotoxic dose (TD50) of 11.8 µg/mL. BpirLAAO-I induced considerable dose-dependent decrease in the T. gondii infection index under two different conditions, treatment of tachyzoites before infection or treatment of HFF cells after infection. A maximal inhibition of infection (56 percent) was found for treatment before infection, with a median inhibitory dose (ID50) at 1.83 µg/mL and selectivity index (SI) at 6.45. For treatment after infection, it was observed a maximal inhibition of infection at 65 percent, ID50 of 1.20 µg/mL and SI of 9.83. The treatment before infection was also effective to reduce intracellular parasitism up to 62 percent, although presenting higher values of ID50 (3.14 µg/mL) and lower values of SI (3.76). However, treatment after infection was not effective, suggesting that the enzyme seems to have no effect on the parasite intracellular replication for this condition. In conclusion, BpirLAAO-I was more effective to inhibit the infection of neighboring cells and consequently parasite dissemination than primary infection and parasite replication. Thus, the effect of BpirLAAO-I described herein could be taken into account for the development of new synthetic anti-parasite therapeutic agents.

Seroprevalence of Toxoplasma gondii infection in goats by the indirect haemagglutination, immunofluorescence and immunoenzymatic tests in the region of Uberlândia, Brazil

A comparative study of the indirect haemagglutination (IHA), immunofluorescence (IFAT) and immunoenzymatic (ELISA) tests was carried out to determine the prevalence of Toxoplasma gondii antibodies in goats. One hundred seventy-four serum samples were obtained from four goat herds from the region of Uberlândia, State of Minas Gerais. The distribution of the animals, according to their origin, was as follow: 71 from herd I; 39 from herd II; 37 from herd III; and 27 from herd IV. Serum samples were analyzed by IHA, IFAT and ELISA, considering the reactivity of the serum samples at dilution ≥ 1:64 as cut off titer for the three tests. A global seroprevalence of 18.4 percent was observed, with significantly higher positivity rate in the herd II (66.7 percent) and older animals (> 36 months). A high and significant positive correlation was found between the titers obtained by the IHA versus IFAT, IHA versus ELISA, and ELISA versus IFAT. Therefore, it can be concluded that the three analyzed tests have shown to be highly concordant and appropriate for epidemiological surveys of Toxoplasma infection in goats. Although the seroprevalence of T. gondii infection in goats is relatively low in this region as compared to other regions of the country, adequate management might be useful and essential to control the infection in the goat herds

Detection of Toxoplasma gondii soluble antigen, SAG-1(p30), antibody and immune complex in the cerebrospinal fluid of HIV positive or negative individuals

Active infection by T. gondii was evaluated by immunoassay for soluble SAG-1 (p30), the major surface antigen from T. gondii, specific antibodies and immune complexes in human cerebrospinal fluid (CSF) samples. A total of 263 samples of CSF were collected from hospitalized patients presenting neurological disorders and analyzed for antibodies to HIV. Patients were divided into two groups: HIV positive (n = 96) or HIV negative (n =167). The results of the assays showed that 45 of all samples were positive for soluble SAG-1. Toxoplasma Ag/Ab immune complexes were detected in 19 of the CSF samples and 62 were positive for T. gondii- specific IgG. A combination of these assays in the presence of clinical findings consistent with active Toxoplasma infection may predict the presence of toxoplasmic encephalitis. Moreover, detection of soluble SAG-1 in the CSF of these individuals appears consistent with active infection.

Experimental infection of Calomys callosus (Rodentia, Cricetidae) by Toxoplasma gondii

Calomys callosus, Renagger 1830 (Rodentia, Cricetidae), a wild rodent found in Central Brazil, was studied to investigate its susceptibility to Toxoplasma gondii experimental infection and its humoral immune response against this protozoa. The electrophoretic profile of the serum proteins of C. callosus showed that IgG, which shows no affinity to Protein A, has higher cross reactivity with rat IgG than with IgG from other rodents. The susceptibility assay was performed by inoculation groups of animals with various suspensions of T. gondii tachyzoites from 10² to 10 6 parasites. All animals died between 3 and 9 days after infection and the kinetics of andibody synthesis was determined. Basically, they recognized predominantly the immunodominant antigen SAG-1 (P30). The immunohistochemistry assays revealed that the liver was the most heavily infected organ, followed by the spleen, lungs, intestine, brain and kidneys. It can be concluded that C. callosus is an excellent experiment model for acute phase of Toxoplasma infection.

Detection of Toxoplasma gondii specific antibodies in dogs: a comparative study of immunoenzymatic, immunofluorescent and haemagglutination titers

We evaluated the titers os anti-T. gondii antibodies by various serological testes in 40 serum samples from dogs exhibiting clinical signs of infectios diseases. Indirect immunoflurescence (IgG-IFI), indirect haemagglutination (IHA and M-Toxo) and immunoenzymatic (ELISA and PA-ELISA) tests were carried out. Titers > 64 were considered as positive. Anti-Toxoplasma antibodies were found in 9 (22.5 per cent), 14 (35 per cent) and 12 (30 per cent) samples, respectively for IHA, IgG-IFI, ELISA and PA-ELISA. The results showed that 57 per cent were negative in all tests and 43 per cent of the dogs presented antibodies to T. gondii; from these, 20 per cent were positive in all three tests with high titers of antibodies and 23 per cent were positive in only one or two tests with low titers of antibodies and mainly related to the IFI and ELISA tests. We observed 5 (12.5 per cent) and 1 (2.5 per cent) reactive samples, respectively, by M-Toxo and IHA with or wihout 2-mercapthoethanol, in the attempt to detect specific IgM. We can conclude that serodiagnosis of toxoplasmosis in dog have to be based on the combination of serological tests (IFI and ELISA) and with emphasis at the determination of the titers and the classes of specific antibodies.